Field of the Invention
The present invention relates to an automatic transmission for a vehicle.
Description of Related Art
Recent increases in oil prices are triggering stiff competition among auto-makers in enhancing fuel consumption of a vehicle.
Therefore, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages.
However, in the case of the automatic transmission, the number of internal components increases as the number of gear shift stages is increased, which may deteriorate installability, production cost, weight and/or power flow efficiency.
Accordingly, development of a planetary gear train which may bring about maximum efficiency with a small number of components is important in order to increase a fuel efficiency enhancement effect through the multiple speed stages.
In this respect, an eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is under investigation.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.